This invention relates to a brake and more particularly, to a brake comprising a base on which are mounted a pair of, usually lined, brake shoes which are normally urged by resilient biasing means into engagement with a drum to apply the brake, and are movable against the force of the resilient biasing means by electromagnetic means to release the brake.
It will be appreciated that in use the linings of the brake shoes wear. Where the electromagnetic means comprises an electromagnet having an armature which moves relative to one or more coils of the magnet, as the shoe linings wear, this increases the gap between the armature and the coil, i.e. the magnet armature gap, when the brake is applied, so that the armature has to move from an increasingly greater distance from the coil when the coil is energised. Unless periodically the brake is adjusted to reduce the armature gap, severe wear of the shoe linings can result in the armature lying beyond the range throughout which the coil can attract the armature against the force of the resilient biasing means which tend to apply the brakes and resist movement of the magnetic armature. Thus the brakes cannot be released.